Powder coating system and method for quick color change

ABSTRACT

A powder coating system includes a booth and one or more powder-recovery modules that are insertable into an equipment-receiving space of the booth. A color change method includes removing a first powder-recovery module from the equipment-receiving space and positioning a second powder-recovery module in the equipment-receiving space.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This patent application claims priority under 35 U.S.C. § 119(e)to U.S. Provisional Patent Application Serial No. 60/242,937, filed Oct.24, 2000, the disclosure of which is hereby incorporated herein byreference.

BACKGROUND AND SUMMARY OF THE INVENTION

[0002] The present invention relates to a powder coating system andparticularly, to a color change booth used in a powder coating system.More particularly, the present invention relates to a color change boothconfigured to permit recovery of powder that fails to adhere to objectsbeing coated in the booth.

[0003] Powder coating systems that operate to apply a coating ofelectrostatically charged particles or powder to an object are known. Atypical powder coating systems includes a booth through which objects tobe coated with powder are conveyed and one or more powder applicatorsthat spray electrostatically charged powder toward the objects to becoated. Some of the particles adhere to the object and some do not.Because powder is fairly expensive, it is desirable to recover thenon-adherent powder for re-use in the powder coating system.

[0004] Powder is available in a variety of colors. When manufacturerschange the color of powder being dispensed by the powder applicator(s),various components of the powder coating system need to be cleaned ifpowder is being recovered in such a way that powder of one color is notinadvertently contaminated with powder of another color so that it canbe reused. It is also highly desirable for the color change process tobe completed quickly to maximize utilization of the powder coatingsystem.

[0005] According to this disclosure, a powder coating system for coatingobjects with powder includes a separator assembly configured to removepowder from an air-powder mixture and a booth in which objects arecoated with powder. The booth has a bottom wall that overlies theseparator. The bottom wall is formed to include an opening through whichthe air-powder mixture moves into the separator assembly. The powdercoating system also includes a hopper assembly that underlies theseparator assembly. The powder removed from the air-powder mixture inthe separator assembly is fed downwardly to the hopper assembly.

[0006] In an illustrative embodiment, the hopper assembly includes a setof wheels that allows the hopper assembly to be wheeled out from underthe bottom wall and the separator assembly is carried by the hopperassembly. Air circulation equipment is included in the powder coatingsystem and operates to draw the air-powder mixture downwardly from thebooth and into separator assembly. The powder coating system includespowder applicators that spray powder to coat the objects and a powderstation that supplies powder to the powder applicators. Powder that isrecovered from the air-powder mixture and fed to the hopper assembly istransferred to the powder station for re-use.

[0007] Also according to this disclosure, the powder coating systemincludes a plurality of powder-recovery modules, each of which isinterchangeably insertable into the equipment-receiving space to receivethe air-powder mixture. Each illustrative powder-recovery moduleincludes a separator assembly and a hopper assembly. When the powdercoating system is changed over from coating objects with powder of afirst color to coating objects with powder of a second color, a first ofthe plurality of powder-recovery modules is removed from theequipment-receiving space and a second of the plurality ofpowder-recovery modules is positioned in the equipment receiving space.

[0008] According to this disclosure, after any one of thepowder-recovery modules are removed from the equipment-receiving spaceduring color changes, the removed powder-recovery module is disassembledand cleaned. Other portions of the powder coating system are cleanedduring color change operations. In the illustrative embodiment, thepowder coating system is designed to permit two workers or operators tocomplete the color change process in 15 minutes or less.

[0009] Additional features of the invention will become apparent tothose skilled in the art upon consideration of the following detaileddescription of a preferred embodiment exemplifying the best mode ofcarrying out the invention as presently perceived.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The invention may best be understood by referring to thefollowing detailed description and accompanying drawings whichillustrate the invention. In the drawings:

[0011]FIG. 1 illustrates a perspective view of a color change systemconstructed according to the invention showing multiple powder-recoverymodules or carts and a spray-to-waste module or cart, all orientedside-by-side near a color change booth and showing a thirdpowder-recovery module or cart situated in an equipment-receiving spaceof the booth;

[0012]FIG. 2 illustrates a top plan view of the system illustrated inFIG. 1;

[0013]FIG. 3 illustrates a partly fragmentary front elevation view of aportion of the powder coating system illustrated in FIG. 1-2, showingthe booth, a powder station to the right of the booth, and aircirculation equipment to the left of the booth;

[0014]FIG. 4 illustrates a partly exploded perspective view of one ofthe powder-recovery carts illustrated in FIG. 1, showing a wheeledhopper assembly, a separator assembly above the hopper assembly, andfirst and second ducts situated along opposite sides of the separatorassembly;

[0015]FIG. 5 illustrates a perspective view of the hopper assemblyillustrated in FIG. 4, showing venturi pumps coupled to the bottoms ofrespective hoppers of the hopper assembly;

[0016]FIG. 6 illustrates a fragmentary perspective view of a detail ofthe booth and powder-recovery cart illustrated in FIG. 1, showing thehopper assembly including a plate to which a number of hoses are coupledand a control panel for the booth;

[0017]FIG. 7 illustrates an enlarged fragmentary perspective view of adetail of the separator assembly illustrated in FIG. 4, showing anair-powder mixture entering a plurality of separator tube assemblies, aquantity of recovered powder moving downwardly out of the separator tubeassemblies, and air that is generally powder-free moving upwardly out ofthe powder tube assemblies;

[0018]FIG. 8 illustrates a fragmentary perspective view of portions ofthe booth and one of the powder-recovery carts illustrated in FIG. 1,showing the booth including lift rails supported relative to a frame ofthe booth by lift actuators. The powder-recovery cart including a pairof catch lips aligned with respective lift rails The powder-recoverycart is illustrated arranged for movement into an equipment-receivingspace of the booth;

[0019]FIG. 9 illustrates a fragmentary front elevation view of a portionof the booth and one of the powder-recovery carts. The cart isillustrated received in the equipment-receiving space of the booth. Thewheels of the cart are illustrated resting on the floor. The uppersurfaces of the ducts are spaced apart from a bottom wall of the booth;

[0020]FIG. 10 illustrates a fragmentary front elevation view similar toFIG. 9 showing the lift actuators actuated to lift the powder-recoverycart so that the wheels of the cart are spaced apart from the floor andso that the upper surfaces of the ducts engage an undersurface of thebottom wall;

[0021]FIG. 11 illustrates a fragmentary sectional view of a portion ofthe booth and one of the powder-recovery carts, taken generally alongsection lines 11-11 of FIG. 10. FIG. 11 illustrates the air-powdermixture moving downwardly from an inner space of the booth into theseparator assembly, recovered powder moving downwardly from theseparator assembly into the hopper assembly, and air moving upwardlyfrom the separator assembly into an air duct of the booth that overliesthe separator assembly;

[0022]FIG. 12 illustrates a fragmentary sectional view of a portion ofthe booth showing doors in the bottom of the booth in open orientations,uncovering openings in the bottom wall of the booth;

[0023]FIG. 13 illustrates an enlarged sectional view of certain detailsof FIG. 12 showing one of the doors moved by its actuator to a closedorientation to facilitate movement of workers around on the floor of thebooth;

[0024]FIG. 14 illustrates a fragmentary perspective view of a portion ofthe booth and one of the powder-recovery carts showing a sensor on thebooth having a lever which protrudes into the equipment-receiving spaceto serve entry of a powder recovery cart into the space;

[0025]FIG. 15 illustrates a perspective view similar to FIG. 14 showingthe powder-recovery cart moved into the equipment-receiving space. Thelever on the sensor is actuated, signaling the presence of thepowder-recovery cart in the equipment-receiving space;

[0026]FIG. 16 illustrates a fragmentary perspective view of a portion ofa powder-management booth showing a container of powder sitting on ashelf of the booth, a plurality of suction tubes in a loweredorientation to extract powder from the container for delivery to thepowder applicators, a sieve having a frustoconical upper portion thatreceives recovered powder from the powder-recovery cart, and a hoseextending from a frustoconical lower portion of the sieve to thecontainer to deliver recovered powder to the container;

[0027]FIG. 17 illustrates a fragmentary perspective view of the samecomponents as to FIG. 16 showing the plurality of suction tubes in araised orientation to permit removal and replacement of the powdercontainer. The lower end of the hose that extends from the sieve isillustrated removed from the container. The container is illustratedmoved off of the shelf to expose an array of air nozzles; and

[0028]FIG. 18 illustrates a fragmentary perspective view of some of thesame components as FIG. 16-17, showing the suction tubes engaging theair nozzles. Air is provided from the nozzles to the suction tubes andother passages in the powder applicators to clean these components ofpowder during color change operations. Components of the sieve areillustrated disassembled to permit cleaning of the sieve components, forexample, with an air gun during a color change operation.

DETAILED DESCRIPTIONS OF ILLUSTRATIVE EMBODIMENTS

[0029] A powder coating system 30 includes a color change booth 10 inwhich objects 26 are coated with particles of powder 28. Powder coatingsystem 30 also includes powder-recovery modules or carts 54 that areeach individually insertable into an equipment-receiving space 24provided by booth 10. Powder coating system 30 further includes a powderstation 300, best illustrated in FIGS. 2 and 3, and powder applicators42, best illustrated in FIGS. 1-3. Powder applicators 42 can be of anyof a member of known types that electrostatically charge and spraypowder 28 provided from powder station 300 toward objects 26 in booth10. Air circulation equipment 258 of powder coating system 30 operatesto create an air stream that flows through booth 10 and the cart 54received in space 24. Some of the sprayed powder 28 adheres to objects26 and some doesn't. The non-adherent powder 28 that becomes entrainedin the air stream flowing through booth 10 forms an air-powder mixture29. Air-powder mixture 29 flows from booth 10 into the powder-recoverycart 54 received in space 24 where powder 28 is separated fromair-powder mixture 29 and returned to powder station 300 for reuse. Whenpowder coating system 30 is changed from coating objects 26 with powder28 of a first color to coating objects 26 with powder 28 of a secondcolor, the cart 54 which has been used in the recovery of the powder 28of the first color is exchanged for another cart 54 which will be usedin the recovery of the powder 28 of the second color, and variouscomponents of powder coating system 30 are cleaned so that powder 28 ofthe first color is not inadvertently mixed with powder 28 of the secondcolor.

[0030] Illustrative color change booth 10 includes a top wall 12, sidewalls 14, end walls 16, and a bottom wall 18 as shown in FIG. 1. Sidewalls 14 and end walls 16 extend substantially vertically between topwall 12 and bottom wall 18. In addition, side walls 14 blend togetherwith end walls 16 to define rounded corner regions of illustrative booth10. Booth 10, therefore, includes a plurality of walls 12, 14, 16, 18that define an interior 20. Booth 10 includes a frame 22, a portion ofwhich is positioned to lie beneath bottom wall 18, as best illustratedin FIG. 1. Frame 22 rests upon a floor and supports bottom wall 18 inspaced apart relation from the floor so that equipment-receiving space24 is defined between bottom wall 18 and the floor.

[0031] By blending walls 14, 16 together at rounded corner regions ofillustrative booth 10, the tendency of powder 28 to accumulate in theseregions is less than if walls 14 and walls 16 intersected at sharpercorners. However, it is within the scope of this disclosure for booth 10to have walls 12, 14, 16, 18 that meet at sharp or blended corners. Inaddition, it is within the scope of this disclosure for walls 12, 14,16, 18 to be made from any type of material having suitable structuralrigidity. However the tendency of powder to accumulate on walls 12, 14,16 is lessened if walls 12, 14, 16 are made from a non-metallicmaterial, such as a transparent resin. In the illustrated embodiment,bottom wall 18 is constructed from a stainless steel material, and thatattracts nonadherent, electrostatically charged powder 28 downwardlytoward it.

[0032] Objects 26 are supported 32 from an overhead conveyor 34 as bestillustrated in FIG. 1. Uncoated objects 26 are moved by conveyor 34 intointerior space 20 of booth 10 where powder 28 is dispensed onto theobjects 26. The objects 26 then continue on conveyor 34 out of interiorspace 20 of booth 10. Top wall 12 of booth 10 includes an elongated slot36 and end walls 16 include openings 38 that accommodates the supports32 by which objects 26 are transported through interior 20.

[0033] As objects 26 move into interior 20 of booth 10 prior to coating,supports 32 enter slot 36 at the front end thereof and objects 26 movethrough opening 38 in front end wall 16. As objects 26 move throughinterior 20 of booth 10 to be coated, supports 32 move through slot 36from the front end thereof to the rear end thereof while carrying theassociated objects 26 through the interior 20 of booth 10 to the rear ofbooth 10. After objects 26 are powder coated, objects 26 exit booth 10through opening 38 in rear end wall 16 and supports 32 exit slot 36 atthe rear end thereof. Booth 10 includes doors 40 that are movablebetween open orientations illustrated in FIG. 1, and closed orientations(not shown).

[0034] Powder coating system 30 includes one or more powder applicators42 as illustrated in FIGS. 1 and 2. Each applicator 42 includes anin/out positioner 50, reciprocator 44 carried by positioner 50, supports46 carried by reciprocator 44, and powder spray guns 48 mounted on thedistal ends of supports 46. Side walls 14 of booth 10 are formed toinclude one or more vertical slots 52, best illustrated in FIG. 1-2.Supports 46 extend from the associated reciprocator 44 through slots 52so that guns 48 are supported in the interior 20 of booth 10.

[0035] When objects 26 are being coated with powder 28, reciprocators 44operate under automatic control, which typically causes guns 48 toreciprocate up and down while electrostatically charged powder 28 issprayed from guns 48 toward objects 26. Movement of guns 48 in thismanner causes the cloud of powder 28 formed in interior 20 to berelatively more uniform, which promotes more even coating of objects 26.In some embodiments, reciprocators 44 also reciprocate guns 48 from sideto side. Positioners 50 also typically operate under automatic controlto project and retract associated reciprocators 44 and guns 48horizontally in and out relative to booth 10. Such horizontal in and outpositioning is desirable, for example, during cleaning operations and tocompensate for changing widths of objects 26 that are being powdercoated. Powder coating system 30 includes one or more control units 54which typically include computers, programmable logic controllers, orthe like that control the operation of reciprocators 44, positioners 50,and guns 48. Control units 54 are illustrated diagrammatically in FIG.2.

[0036] It will be appreciated that many different types ofreciprocators, positioners, and guns may be used in powder coatingsystem 30. For example, ITW Gema of Indianapolis, Ind. manufacturesmodel no. ACR and ZA 1 reciprocators; a model no. XT-6 positioner, andmodel no. PG-2A and model no. PG-2AX guns, all of which are suitable foruse in such powder coating systems 30. It is also within the scope ofthis disclosure for stationary guns that spray powder toward objects 26to be included in powder coating system 30 in lieu of, or in additionto, applicators 42. Such stationary guns or nozzles can be mounted tobooth 10 or to other supporting structure situated alongside booth 10.It will also be appreciated that minimizing the surface area of walls12, 14, 16, 18 on which powder 28 can accumulate reduces the amount oftime it takes to clean walls 12, 14, 16, 18 during color changeoperations.

[0037] Illustrative booth 10 does not include any manual powderapplicator equipment. To the extent that manual powder coatingoperations are required for any of objects 26, it is contemplated thatsuch manual powder coating operations be conducted in a separatespray-to-waste booth (not shown) that does not need to be cleaned duringcolor change operations. Of course, manual powder coating equipment canbe included in booth 10, if desired. Therefore, the present disclosureis not limited to booths having only automatic powder coating equipment.

[0038] Powder coating system 30 includes multiple mobile powder-recoverymodules or carts 54, each of which is configured to be received inequipment-receiving space 24, as best illustrated in FIGS. 1 and 2. Whenit is received in equipment-receiving space 24, one of thepowder-recovery carts 54 functions to recover powder 28 from theentraining air stream 29 that enters the cart 54 from interior 20. Whenpowder coating system 30 is changed from coating objects 26 with powder28 of a first color to coating objects 26 with powder 28 of a secondcolor, the cart 54 received in equipment-receiving space 28 to separatepowder 28 of the first color from the associated air-powder mixture 29is moved out of equipment-receiving space 24 and another cart 54assigned to separate powder 28 of the second color from an entrainingair stream 29 is moved into equipment-receiving space 24. Thus, carts 54are exchanged during color change operations.

[0039] Turning now to the construction of carts 54, and with particularreference to FIGS. 4-11 and 14-16, each cart 54 includes a hopperassembly 56, a separator assembly 58 carried by hopper assembly 56, and60 that couple to separator assembly 58 as illustrated, for example, inFIG. 4. Carts 54 are modular. That is, associated hopper assemblies 56,separator assemblies 58, and ducts 60 are transportable together as aunit and are movable into and out of space 24 as a unit. Therefore, thedescriptions that follow of the hopper assembly 56, separator assembly58, and ducts 60 of one illustrative cart 54 apply to other carts 54 aswell, unless specifically noted otherwise.

[0040] Illustrative hopper assembly 56 includes an upper frame 76 havinga pair of longitudinally extending side frame members 78 and a pair oftransversely extending end frame members 80 as illustrated in FIGS. 4and 5. Frame members 78 cooperate with frame members 80 to define arectangle. Frame 76 also includes four struts 74 that extend generallyparallel to frame members 80 between frame members 78 struts 74 aresubstantially uniformly spaced between frame members 80. Illustrativehopper assembly 56 also includes large hoppers 62 and a small hopper 64situated between hoppers 62/See FIG. 11. Hoppers 62, 64 extenddownwardly from an underside of frame 76.

[0041] Hoppers 62, 64 have side walls 66 that are generally triangularin shape and end walls 68 that are generally trapezoidal in shape. Eachof hoppers 62, 64 includes a generally vertical by extending upper lip67 by which that hopper 62, 64 is mounted to frame 76. Surrounding lip67 of each hopper 62 thus defines a somewhat square-shaped openings 70and lip 67 of hopper 64 defines a somewhat rectangular opening 71.Hoppers 62, 64 thus define within their interiors powder-collectionchambers 72, best illustrated in FIG. 11, beneath respective openings70, 71. Two of struts 74 extend across respective openings 70 and two ofstruts 74 lie between respective openings 70 and opening 71 as bestillustrated in FIGS. 4 and 5.

[0042] Hopper assembly 56 includes four legs 82, two of which extenddownwardly from end wall 68 associated with hopper 62 at the front endof hopper assembly 56 and two of which extend downwardly from end wall68 associated with hopper 62 at the rear end of hopper assembly 56. Thelower ends of respective legs 82 are provided with casters 84 asillustrated, for example, in FIG. 4. Hopper assembly 56 also includes ahandle 86 connected by arms 88 to the two of legs 82 at the front end ofhopper assembly 56. Thus, powder-recovery carts 54 are made mobile andare easily movable around a powder coating facility.

[0043] Hopper assembly 56 includes a longitudinally extending channelmember 90 mounted to side walls 66 of hoppers 62, 64 as best illustratedin FIG. 4. A vibrator 92, such as an eccentric motor, is mounted tomember 90 and is operable to vibrate hoppers 62, 64 to facilitatemovement of powder 28 collected in hoppers 28 to the bottoms ofpowder-collection chambers 72. A vibrator 92 controller 94 is mounted toone of legs 82 at the front end of hopper assembly 56. A power cable 96extends from controller 94 to a power source (not shown) in aconventional manner. A control cable 98 extends between controller 94and vibrator unit 92. Controller 94 turns vibrator unit 92 on and offand controls the frequency with which vibrator unit 92 vibrates hoppers62, 64.

[0044] The lower ends of walls 66 of hoppers 62, 64 include openings 100as illustrated, for example, in FIG. 11. Each cart 54 includes a set ofpowder transfer units 110 mounted to the bottom ends of hoppers 62, 64as best illustrated in FIG. 5. Each powder transfer unit 110communicates with a respective powder-collection chambers 72 through arespective associated openings 100. Illustrative powder transfer units110 are venturi pumps. In other embodiments of cart 54, powder transferunits 110 may be any other types of devices capable of extracting therecovered powder 28 from chambers 72 and moving powder 28 back to powderstation 300. Illustrative hopper assembly 56 includes a set of outlettubes 112, illustrated in FIGS. 9 and 10, that couple respectiveopenings 100 to respective venturi pumps 110. Venturi pumps 110communicate with respective chambers 72 through associated tubes 112 andopenings 100.

[0045] Hopper assembly 56 includes a manifold plate 114 mounted at aconvenient location on hopper assembly 56 as illustrated best in FIG. 6.A high-pressure air inlet port 116 and powder tube ports 118 extend fromplate 114 as illustrated in FIGS. 4 and 6. A high-pressure air hose 120is coupled to port 116 to deliver high-pressure air from a pressuresource (not shown) to cart 54. A three-way splitter 124 on the back sideof plate 114 receives high-pressure air through port 116 and delivershigh-pressure air to associated air-delivery hoses 122 which extend fromsplitter 124 to respective venturi pumps 110. Hopper assembly 56 alsoincludes three powder-transfer hoses 126 that extend between outlets ofassociated venturi pumps 110 and respective powder tube ports 118.High-pressure air delivered to venturi pumps 110 via hoses 122 passesthrough venturi pumps 110 powder 28 accumulated in the bottoms ofchambers 72 for transport back to powder station 300. The constructionand operation of venturi pumps and dense phase conveyors is well knownto those skilled in the art.

[0046] Separator assembly 58 is situated above and is carried by hopperassembly 56. Frame 76 of hopper assembly 56 has upper surfaces that aresubstantially coplanar with upper surfaces of struts 74 as illustratedin FIGS. 4 and 5. Separator assembly 58 rests upon the upper surfaces offrame 76 and struts 74. Hopper assembly 56 includes a plurality of tabs128 extending upwardly from frame 76 to facilitate orienting andretention of separator assembly 58 on hopper assembly 56. Separatorassembly 58 receives air-powder mixture 29 from ducts 60, separatespowder 28 from air-powder mixture 29, and delivers the separated powder28 to chambers 72 for recovery.

[0047] Illustrative separator assembly 58 includes five, side-by-sideseparator modules 130, as best illustrated in FIG. 4. Referring to FIGS.4 and 7 each module 130 includes an upper panel 132, a box 134underlying panel 132 in spaced-apart relation therewith, a plurality ofsupports 133 connecting panel 132 and box 134 at corners thereof, and aplurality of vertically extending separator tube assemblies 136 coupledto panel 132 and box 134. Each box 134 includes a rectangular top wall138, a rectangular bottom wall 140, a pair of long walls 142, and a pairof short walls 144. Boxes 138 are sized so that when modules 130 arecarried by hopper assembly 56, walls 142 lie above respective struts 74or end frame members 80 and walls 144 lie above respective portions ofside frame members 78.

[0048] Each panel 132 is formed to include a plurality of openings 146and upper ends of associated tube assemblies 136, sealingly engage anunderside of panel 132 in the regions around respective openings 146 asshown in FIG. 7. Top wall 138 of each box 134 is formed to include aplurality of openings 148, each of which receives a middle portion of arespective tube assembly 136, and bottom wall 140 of each box 134 isformed to include a plurality of openings 150, each of which receives alower portion of a respective tube assembly 136. Thus, each one ofopenings 148 is vertically aligned with an associated opening 146 and anassociated opening 150

[0049] Each separator tube assembly 136 includes a cylindrical uppertube 152 and a lower tube 154. Each lower tube 154 includes acylindrical upper portion and a frustoconical lower portion. Thecylindrical upper portion of each lower tube 154 has a larger diameterthan the associated upper tube 152 and a lower portion of each uppertube 152 is received in the cylindrical upper portion of a respectivelower tube 154. Each separator tube assembly 136 further includes aplurality of deflecting vanes 156 at the upper end of lower tube 154.Vanes 156 extend radially between corresponding tubes 152, 154 andmaintain tubes 152, 154 together in a coaxial configuration. Upper edges158 of vanes 156 are substantially coplanar with an upper ends 160 ofrespective lower tubes 154. Vanes 156 terminate at lower edges 162spaced from upper edges 158. Vanes 156 are configured to deflect theair-powder mixture 29 which encounters them in a somewhat spiral orhelical flow which causes powder 28 from in air-powder mixture 29 to bethrown radially outwardly by centrifugal force. Thus, separator tubeassemblies 136 are sometime referred to as cyclone separators. Gravitythen causes the separated powder 28 to drop downwardly through thefrustoconical lower portion of tubes 154 and out of openings 166 intohopper assembly 56. As powder 28 moves downwardly, the air fromair-powder mixture 29 is recovered by being drawn upwardly through tubes152 by air circulation equipment 258 as will be discussed in furtherdetail below.

[0050] Illustrative separator assembly 58 includes five separatormodules 130 that are arranged in side-by-side relation so that longwalls 142 of adjacent boxes 134 confront one another. Frame members 78,80 and struts 74 support modules 130 above powder-collection chambers 72so that powder 28 separated from air-powder mixture 29 by separator tubeassemblies 136 falls downwardly through openings 168 into the associatedchamber 72. The middle separator module 130 is situated above chamber 72defined within hopper 64. The two separator modules 130 in front of themiddle separator module 130 are situated above the front hopper 62 andthe two separator modules 130 to the rear of the middle separator module130 are situated above the rear hopper 62 as illustrated in FIG. 4.Gaskets or other suitable sealing members can be interposed betweenbottom walls 140 of boxes 134 and the corresponding struts 74 and framemembers 78, 80. Separator assembly 58 includes a pair of vertical,transversely extending end plates 168 that are situated at opposite endsof separator assembly 58 above top walls 138 of the boxes 134 of the twoend modules 130 as illustrated in FIG. 4. End plates 168 are configuredto close the opposite ends of the space defined between panels 132 andtop walls 138 of boxes 134 of the endmost separator modules 130. In someembodiments, gaskets or other suitable sealing members are interposedbetween end plates 168 and modules 130.

[0051] Ducts 60 each include an upwardly facing rectangular surface 170defining an inlet opening 172 and a vertically oriented rectangularsurface 174 defining an outlet opening 176 as illustrated best in FIG.4. Ducts 60 also each include a pair of end walls 178, a curved innerwall 180, and a curved outer wall 182. Walls 180, 182 extendlongitudinally of cart 54 between walls 178. Thus, walls 178, 180, 182of each duct 60 provide a curved passage between openings 172, 176.Separator assembly 58 includes a plurality of attachment devices, eachof which includes a first portion 184 mounted to a respective end wall178 of an associated duct 60 and a second portion 186 mounted to arespective end plate 168. Clamping assemblies 184, 186 selectivelycouple ducts 60 to separator assembly 58. When ducts 60 are coupled toseparator assembly 58, the curved passages of ducts 60 communicate withthe opposite sides of the space defined between panels 132 and top walls138 of boxes 134 of modules 130. Gaskets (not shown) or other suitablesealing members may be provided on each of rectangular surfaces 170,174.

[0052] Bottom wall 18 of booth 10 is formed to include a pair ofelongated openings 188 as illustrated best in FIGS. 2, 3, 9, 10, 12 and13. Interior 20 is in gas-flow communication with equipment-receivingspace 24 through openings 188. When powder-recovery carts 54 arereceived in space 24, openings 172 of the associated ducts 60 arevertically aligned with openings 188. Each of openings 188 is bounded bya front end or edge 192, a rear end or edge 194, and a pair oflongitudinal sides or edges 196 that extend between front and rear edges192, 194. Front edges 192 of openings 188 are spaced apart from thefront end of bottom wall 18 and rear edges 192 of openings 188 arespaced apart from the rear end of bottom wall 18.

[0053] Booth 10 is configured so that slot 36 formed in top wall 12 isparallel with openings 188 and over the middle region of bottom wall 18.Thus, objects 26 moving through interior 20 of booth 10 on supports 32pass generally over the middle region of bottom wall 18. Air circulationequipment 258 operates to create a downdraft on opposite side of objects26 so that a significant amount of the nonadherent powder 28 in booth 10is swept away downwardly through openings 188, ducts 60, and intohoppers 62, 64.

[0054] Referring now to FIGS. 1, 3 and 8-13 frame 22 of booth 10includes a pair of rectangular lower frame portions 198 each having apair of side frame members 200 and a front frame member 210 as shown inFIG. 1. Frame 22 further includes a rear frame member 212 coupled to therear ends of side frame members 200. A middle portion of rear framemember 212 bridges the space between frame portion 198 as illustrated inFIG. 8. Frame 22 also includes vertical frame members 214, each of whichextends upwardly from an outside corner of each frame portion 198 tosupport walls 12, 14, 16, 18. Leveling pads 216 are provided on frameportions 198 at appropriate locations to level booth 10. Equipmentreceiving space 24 is defined between frame portions 198 at the front ofbooth 10.

[0055] Booth 10 includes actuators 220 mounted by brackets 222 toassociated side frame members 200 as illustrated in FIG. 8. Booth 10further includes a pair of lift rails 224 mounted on respective pairs ofactuators 220. In the illustrative embodiment, actuators 220 arepneumatic piston-and-cylinder actuators which are supplied withcompressed gas and vented through pneumatic lines 230, as is well-knownto those skilled in the art. It will be appreciated that other types ofactuators 220, including electrically powered actuators, hydraulicactuators, motors, and other electromechanical devices in combinationwith transmission elements or linkages, may be used. Each lift rail 224includes a vertical first side surface 234 facing toward theequipment-receiving space 24, a vertical second side surface 235 facingaway from the center region of equipment receiving space 24, and aguiding surface 236 that angles outwardly from surface 234 toward thefront of booth 10. Side frame members 78 of hopper assembly 56 are eachformed to include a catch lip 238 that extends longitudinally of frame76. Each catch lip includes a top portion 240 extending laterallyoutwardly from frame 76 and a side portion 242 extending downwardly fromthe respective top portion 240.

[0056] As powder-recovery cart 54 initially moves intoequipment-receiving space 24 in the direction of arrow 243, FIG. 8,guiding surfaces 236 help to guide cart 54 into proper alignment withbooth 10. As cart 54 moves further into space 24 in direction 243, catchlips 238 move over respective lift rails 224. Legs 82 at the rear end ofcart 54 engage the middle portion of rear frame member 212 upon fullinsertion of cart 54 into space 24. When cart 54 is fully inserted intospace 24, openings 172 of ducts 60 are vertically aligned underneathopenings 188 in bottom wall 18.

[0057] Referring to FIGS. 3 and 9-12 booth 10 includes an air plenum orduct 244 coupled to an underside of the middle region of bottom wall 18between openings 188. Air plenum 244 has a planar bottom surface 246.Air plenum 244 has a large opening formed in bottom surface 246 andseparator assembly 58 is situated beneath this large opening when cart54 is inserted fully into space 24. Air plenum 244 further includes aninclined front panel 248 and a rectangular-to-round transition ductsection 250. Inclined panel 248 is configured to provide a uniformlyincreasing cross sectional duct area toward duct section 250, therebypromoting laminar flow of air from the cart 54 as the air moves into andthrough plenum 244.

[0058] After cart 54 is fully inserted into space 24 underneath bottomwall 18 of booth 10, actuators 220 are actuated to lift cart 54 upwardlyinto sealing engagement with booth 10. As actuators 220 move from theretracted positions to the extended positions, lift surfaces 232 ofrespective lift rails 224 come into contact with top portions 240 ofrespective catch lips 238 to lift cart 54 upwardly from a loweredposition, illustrated in FIG. 9, to a raised position, illustrated inFIGS. 10 and 11.

[0059] Initially, before a cart 54 is lifted into orientation to beconnected to booth 10 to recover powder, rectangular surfaces 170 ofducts 60 are spaced apart from bottom wall 18 by a small distance 252(FIG. 9) and top walls 138 of separator modules 130 are spaced apartfrom bottom surface 246 of air duct 244 by a small distance 254. In someembodiments, distance 252 may be substantially the same as to distance254 so that, as actuators 220 raise cart 54, sealing engagement of ducts60 with bottom wall 18 and sealing engagement of separator assembly 56with surface 246 of air plenum 244 occurs simultaneously. In otherembodiments, gaskets having different thicknesses may be interposedbetween ducts 60 and bottom wall 18 on the one hand and between air duct244 and separator assembly 56 on the other hand, and distances 252, 254need not be substantially equivalent. In such embodiments, as actuators220 raise cart 54, sealing engagement between ducts 60 and bottom wall18 may occur either before or after sealing engagement between air duct244 and separator assembly 56 depending upon differences in thethicknesses of the gaskets or sealing members used. Thus, interposinggaskets or other suitable sealing members between booth 10 and cart 54permits distances 252, 254 to be different.

[0060] After cart 54 is lifted upwardly into engagement with booth 10,casters 84 are spaced above the floor by a distance 256 (FIGS. 10 and11). Distance 256 is substantially the same as whichever of distances252, 254 is smaller, because once cart 54 moves upwardly by an amountsufficient to close the smaller one of distances 252, 254, cart 54 isunable to move upwardly any further to close the larger of distances254. Of course, if distances 252, 254 are substantially equal, thendistance 256 will also be substantially equal to distances 252, 254.

[0061] Various gaskets or sealing members are typically interposedbetween certain elements of cart 54 and between certain portions of cart54 and booth 10. In embodiments having such gaskets or sealing members,these may be constructed from urethane, such as microcellular urethane,or a similar material having appropriate resiliency and sealingproperties. In addition, the gaskets or sealing members may includepressure sensitive adhesives on their contact surfaces. In suchembodiments, the pressure sensitive adhesive enables the gasket to whichit is applied to be adhered to the associated portion of booth 10 orcart 54.

[0062] Powder coating system 30 includes air circulation equipment 258that is coupled to air plenum 244 of booth 10 by duct work 260 asillustrated in FIGS. 2 and 3. Air circulation equipment 258 includes ahousing 261 and a fan 262 having a motor 263 at the top of housing 261.Fan 262 is turned by motor 261 to draw air into and through inner space20 of booth 10, into and through separator assembly 58 ofpowder-recovery cart 54, into and through air plenum 244 of booth 10,and into and through duct work 260. Air indicated by arrows 264 beingdrawn into inner space 20 of booth 10 moves from outside of booth 10 andthrough slot 36 and openings 38 as illustrated in FIG. 3.

[0063] As air 264 moves through inner space 20 of booth 10, powder 28exiting from guns 48 which does not adhere to articles 26 becomesentrained in air 264 to form air-powder mixture 29. Air-powder mixture29 is drawn by air circulation equipment 258 through openings 188 ofbottom wall 18 and through openings 172 into ducts 60 and then throughopenings 176 into the space defined between panels 132 and boxes 134 ofseparator modules 130. As described above with regard to FIG. 7,air-powder mixture 29 moves through openings 148 formed in top walls 138of boxes 134 into separator tube assemblies 136 where powder 28 isseparated from air-powder mixture 29 and is fed downwardly to hopperassembly 56 for recovery. Air from the air-powder mixture 29 that entersseparator tube assemblies 136 moves upwardly through tubes 152 asindicated by arrows 266 in FIGS. 7 and 11 after powder 28 is separatedtherefrom .

[0064] Air circulation equipment 258 draws air 266 from air-powdermixture 29 upwardly through tubes 152 and into air plenum 244 throughopenings 146 formed in panels 132 of separator modules 130. It will beappreciated that, while separator tube assemblies 136 are configured toseparate a significant amount of powder 28 from air-powder mixture 29, asmall percentage of powder 28 from air-powder mixture 29 may still beentrained in the air 266 that moves upwardly from tubes 154 into airplenum 244. Thus, the air 266 moving upwardly through tubes 154 ofseparator tube assemblies 136 and into air plenum 244 is generally, butnot completely, powder-free.

[0065] Air circulation equipment 258 draws air 266 through air plenum244 and into duct work 260. Once air 266 reaches air circulationequipment 258, air passes through a filter section 268 of aircirculation equipment 258. Filter section 268 has a set of filters 270that, in some embodiments, are high-efficiency cartridge filters, suchas HEPA filters, capable of filtering 0.5 micron particles at 99.999%efficiency. Air circulation equipment 258 includes a cleaning systemthat, from time to time, directs blasts of high pressure air at filters270 to dislodge the powder 28 that accumulates in filters 270. Forexample, in one embodiment, each high-pressure air blast is about 0.1seconds in duration. The cleaning air blasts occur about every 15seconds during the operation of fan 262. The dislodged powder 28 fallsdownwardly to a waste hopper 277 of air circulation equipment 258 forcollection and disposal.

[0066] After air 266 is filtered by filters 270 in filter section 268,fan 262 discharges the filtered air into a return duct 272 and moves thefiltered air to a final filter section 274. Final filter section 274includes a plurality of filters 276 that, in some embodiments, are ableto filter 0.5 micron particles at 95% efficiency. Even though filters270 in filter section 268 have very high efficiency, over a long periodof time, the efficiency of filters 270 may decrease such that somepowder 28 may find its way past filters 270. In addition, if any filter270 has a compromised seal or a rupture, then powder 28 entrained in theair will pass through filters 270. Thus, filters 276 in final filtersection 274 are configured to capture most of any powder 28 passingthrough filters 270 prior to discharge of the air back into the ambientenvironment.

[0067] As illustrated diagrammatically in FIG. 3, air circulationequipment 258 can be positioned on one side of a wall 278 of amanufacturing facility and many of the other pieces of equipment ofpowder recovery system 30, such as booth 10 and carts 54, are positionedon the other side of wall 278. Wall 278 can provide a barrier to same ofthe noise generated by fan 262 and the cleaning system of aircirculation equipment 258 from reaching the area of the manufacturingfacility in which booth 10 resides.

[0068] Fan 262 normally operates to move a sufficient volume of air at asufficient rate into booth 10 to prevent powder 28 sprayed from guns 48from exiting booth 10 through slot 36 and openings 38. In addition,illustrative separator tube assemblies 136 operate at high efficienciesto separate powder 28 from air-powder mixture 29. In an illustrativesystem the volume flow rate of air-powder mixture 29 drawn into eachseparator tube assembly 136 is in the range of about 17 cubic feet perminute to about 21 cubic feet per minute. Illustrative separator modules130, each having 76 separator tube assemblies 136, separate a highpercentage of powder 28 from air-powder mixture 29 if about 1500 cubicfeet of air per minute is drawn through each module 130. Thus, in theillustrative embodiment in which carts 54 each have five separatormodules 130, fan 262 is selected to move about 7500 cubic feet of airper minute through booth 10 and cart 54. This air flow rate contains thepowder 28 sprayed from guns 48 in booth 10 and also separator modules130 to have efficiencies consistently greater than 95%.

[0069] Air circulation equipment 258 includes a number of gages,pressure switches and sensors (not shown) to sense air velocities andpressures at various points in the air flow passages of air circulationequipment 258. Depending upon the velocities and pressures sensed, thespeed at which motor 263 of fan 262 operates can be adjusted to maintainthe appropriate volume flow rates of air flow throughout powder coatingsystem 30. In addition, if certain sensors sense that the pressure dropacross, for example, filters 270 or filters 276 exceeds a certainamount, a warning indicator, such as a light or an image on a displayscreen, may be activated to indicate that filters 270 or filters 276, asthe case may be, will soon need to be replaced. If the sensors sensethat the pressure drop across filters 270 or filters 276 is too great,which indicates a heightened risk that powder containment in booth 10may be lost, then a signal can be sent to shut down powder coatingsystem 30 altogether. If powder coating system 30 is shut down in thismanner, the reason for the shutdown can also be displayed on a displayscreen.

[0070] Powder 28 that is separated from air-powder mixture 29 byseparator assembly 58 and that accumulates in the bottom of chambers 72of hoppers 62, 64 is moved by powder transfer units 110, such asillustrative venturi pumps 110, back to powder station 300 as describedabove. Illustrative powder coating system 30 includes a set of hoses 280that extend between cart 54 and powder station 300 as shown in FIG. 3.First ends of each of hoses 280 are coupled to ports 118 extending fromplate 114 of the cart 54 situated in space 24. Powder station 300includes a sieve 310, illustrated in FIGS. 3 and 16-18. Second ends ofhoses 280 are coupled to sieve 310. Each of hoses 126 extending fromillustrative venturi pumps 110 communicates with a respective hose 280through an associated port 118.

[0071] Referring now to FIGS. 16-18, during a coating operation acontainer 312 of powder 28 rests upon a shelf 314 of powder station 300.Powder station 300 includes a hose 316 that extends from the bottom ofsieve 310. An open, distal end of hose 316 is placed in container 312.Powder 28 that accumulates in chambers 72 of hoppers 62, 64 is moved bypowder transfer units 110 through hoses 126, through ports 118, throughhoses 280, through sieve 310, through hose 316 and is returned tocontainer 312. Sieve 310 includes a frustoconical upper portion 317, afrustoconical lower portion 319, a filter screen 318 that is interposedbetween portions 317, 319 as shown in FIG. 18, and a band 321 thatcouples portions 317, 319 together as shown in FIGS. 16 and 17. Filterscreen 318 is configured to permit particles of powder 28 to passtherethrough while blocking any foreign contaminants that are largerthan the screen mesh to prevent them from reaching container 312.Recovered powder 28 is then recycled back through powder applicators 42to coat objects 26.

[0072] As described previously, when powder coating system 30 is changedover from coating objects 26 with powder 28 of a first color to coatingobjects 26 with powder 28 of a second color, the cart 54 situated inequipment-receiving space 24 during powder coating operations with thepowder 28 of the first color (hereinafter “first cart 54”) is removedfrom space 24 and a new cart 54 (hereinafter “second cart 54”) is movedinto space 24. Prior to removal of first cart 54 from space 24, guns 48of powder applicators 42 are turned off to permit one or more operatorsto perform certain cleaning operations as described below. In addition,conveyor 34 is operated to clear objects 26 out of booth 10.

[0073] After guns 48 are turned off so that no more powder 28 is beingsprayed into booth 10, an operator uses a squeegee, dry mop, broom, orother similar device (not shown) to clear bottom wall 18 of loose powder28 by sweeping powder 28 from bottom wall 18 into openings 188. Duringthis initial cleaning operation, air circulation equipment 258 continuesto operate so that the powder swept through openings 188 into thepowder-recovery cart 54 thereunder is recovered. In addition, theoperator sweeping the powder 28 on bottom wall 18 into openings 188inserts the squeegee, broom, etc. into inner space 20 of booth 10through the opening 38 at the front of booth 10 while standing on thefloor in front of booth 10. After bottom wall 18 is cleared of loosepowder 28, air circulation equipment 258 is turned off and first cart 54is removed from space 24.

[0074] To remove first cart 54 from equipment-receiving space 24,actuators 220 are moved from the extended positions to the retractedpositions so that first cart 54 is moved from the raised position,illustrated in FIGS. 10 and 11, to the lowered position, illustrated inFIG. 9. After first cart 54 is moved to the lowered position, hoses 120,280 are disconnected from respective ports 116, 118, power cable 96 isdisconnected from the power source, and first cart 54 is wheeled out ofspace 24 for cleaning. First cart 54 can be disassembled so that ducts60, separator modules 130, and hopper assembly 56 can be cleanedseparately. Portions of clamping devices 184, 186 are manipulated topermit disconnection of ducts 60 from separator assembly 58. After ducts60 are disconnected, separator modules 130 can be lifted off of hopperassembly 56. Any powder 28 on ducts 60, separator modules 130, andhopper assembly 58 can be cleaned using various cleaning devices,including high pressure air guns, vacuum cleaners, and manual cleaningdevices, such as cloths, brooms, mops, and the like.

[0075] Booth 10 includes a pair of doors 290, each of which is supportedwith respect to bottom wall 18 for movement between a first positionclosing a respective opening 188, as illustrated in FIG. 13, and asecond position away from the respective opening 188, as illustrated inFIG. 12. Booth 10 includes longitudinally extending frame members 294and hinges 292. Each hinge 292 includes a first hinge half 293 coupledto bottom wall 18 by a respective frame member 294 and a second hingehalf 295 coupled to a respective door 290. Each hinge half 295 is pinnedto an associated hinge half 293 for pivoting movement about acorresponding longitudinally extending pivot axis 296. Pivot axes 296are parallel with the longitudinal dimensions of respective openings188.

[0076] Booth 10 further includes actuators 286 that operate to movedoors 290 between the first and second positions. In the illustrativeembodiment, actuators 286 are pneumatic actuators, each having acylindrical housing 285 and a piston that projects and retracts a rod287 out of and into the associated housing 285 in a conventional mannerwhen air is supplied to or exhausted from the housing 285. Each actuator286 is pivotably coupled between a member 288 of frame 22 and anassociated door 290. Movement of actuators 286 between extendedpositions and retracted positions moves the respective doors 290 betweenthe first and second positions.

[0077] It will be appreciated that other types of actuators, includingelectrically powered linear actuators, hydraulic actuators, motors, andother electromechanical devices in combination with transmissionelements or linkages, may be used in lieu of pneumatic actuators. Thus,the term “actuator” or “actuators” as used in the specification and inthe claims is intended to cover all of these types of actuators, as wellas the equivalents thereof unless otherwise specified.

[0078] Each door 290 includes a fillet 289 having an upper surface 291.In addition, each door 290 includes a portion 298 that offsets fillet289 away from hinge half 295 so that, when doors 290 move to therespective second positions, fillets 289 move downwardly and outwardlyaway form the central region of space 24 by a sufficient amount toaccommodate receipt of ducts 60 beneath openings 188. Fillets 289 arereceived in respective openings 188, with the result that surfaces 291of fillets 289 are substantially coplanar with the upper surface ofbottom wall 18 when doors 290 are in the first positions as illustratedin FIG. 13. When doors 290 are in the first positions, fillets 289 fillalmost all of the space bounded by edges 192, 194, 196 which definerespective openings 188. Sufficient clearance exists between fillets 289and edges 192, 194, 196 to facilitate the movement of doors 290 intotheir first positions.

[0079] After first cart 54 is removed from space 24 and doors 290 aremoved to the first positions to close openings 188, the operator entersbooth 10 through opening 38 at the rear of booth 10. Because walls 12,14, 16, 18 of booth 10 are elevated above the floor by frame 22, a setof stairs 282 and a landing 284 at the top of stairs 282 are provided atthe rear of booth 10 to facilitate the operator's entry into inner space20 of booth 10. Stairs 282 and landing 284 are illustrated in FIG. 2.After the operator enters inner space 20 of booth 10, doors 40 are movedto the closed positions and the operator cleans the surfaces of walls12, 14, 16, 18 and doors 40 that face toward inner space 20 byvacuuming, mopping and the like. As illustrated in FIG. 13, receipt offillets 289 in openings 188 levels the bottom wall 18 when doors 290 aremoved to their closed positions.

[0080] Booth 10 includes a control panel 330, best illustrated in FIGS.6, 14 and 15, at the front end of booth 10 and a sensor 320, bestillustrated in FIGS. 14 and 15, coupled to a frame member 322 behindcontrol panel 330. Control panel 330 includes a first switch 332 thatcontrols the extension and retraction of actuators 220, a second switch334 that controls the extension and retraction of actuators 286, and apressure regulator 336 that controls delivery of high pressure airthrough hose 120, port 116, splitter 124, and hoses 122 to venturi pumps110. A high-pressure air port 338 is also provided on control panel 330as a connection point for various devices, such as high-pressure airguns (not shown), that require high pressure air for operation.

[0081] Pushing switch 332, moves actuators 220 to extended positions toraise lift rails 224. Pulling switch 332 outwardly moves actuators 220to retracted positions to lower lift rails 224. When no cart 54 ispresent in space 54, pushing switch 334 inwardly moves actuators 286 toextended positions to raise doors 290 to the first positions to closeopenings 188. Pulling switch 336 outwardly moves actuators 286 toretracted positions to move doors 290 away from openings 188. Adjustingpressure regulator 336 changes the pressure of air supplied to venturipumps 110 through hose 120, port 116, splitter 124, and hoses 122.Control panel 330 includes a gauge 340 that provides a booth operatorwith a visual indication of the pressure being supplied to venturi pumps110.

[0082] Sensor 320 senses the presence of a cart 54 in space 24. In theillustrative embodiment, sensor 320 has a lever 324 that is biased to asubstantially vertical orientation extending into equipment-receivingspace 24, as illustrated in FIG. 14. When a cart 54 is moved into space24, the cart 54 engages lever 324 moving it away from the verticalorientation, as illustrated in FIG. 15. When a cart 54 moves lever 324in this manner, a signal is provided to controller circuitry of booth 10that prevents movement of doors 290 from the second positions to thefirst positions. Thus, if switch 334 is pushed when a cart 54 is inspace 24, actuators 286 will not move from the retracted positions tothe extended positions.

[0083] After the operator finishes cleaning doors 40 and walls 12, 14,16, 18 in inner space 20 of booth 10, doors 40 are opened and theoperator exits booth 10. Then, after the operator exits booth 10 andbefore second cart 54 is moved into space 24, switch 334 is pressed tomove doors 290 from the first positions to the second positions. Oncedoors 290 are moved to the second positions, second cart 54 is pushedinto space 24. Switch 332 is pressed to raise second cart 54 intosealing engagement with booth 10. Hoses 120, 280 are connected torespective ports 116, 118 of second cart 54, either before or aftersecond cart 54 is raised by actuators 220.

[0084] Various portions of powder station 300 and powder applicators 42are cleaned when powder coating system 30 undergoes a color change. Asecond operator may attend to the cleaning of powder station 300 andpowder applicators 42 while the first operator cleans booth 10 andexchanges carts 54. Illustrative powder coating system 30 is designed topermit two operators to complete the color change process in 15 minutesor less.

[0085] In the illustrative embodiment, many of the cleaning operationsof powder station 300 and powder applicators 42 are done under automaticcontrol and therefore, the worker attending to the cleaning of thesepieces of powder-delivery equipment 42, 300 does so, in large part, byentering various cleaning commands via a user input device, such as acomputer keyboard or a touch-screen display. For example, such a userinput device 326 coupled to an upper portion of a housing 328 of powderstation 300 is illustrated diagrammatically in FIG. 3. When the operatorselects a cleaning mode by entering inputs on device 326, powderdelivery to guns 48 is stopped and the components of guns 48 that causepowder 28 to be electrostatically charged are turned off. Reciprocators44 and positioners 50 automatically move to cleaning positions. A numberof high-pressure air nozzles (not shown) are coupled to booth 10 in thevicinity of vertical slots 52. Positioners 50 move guns 48 cyclically inand out under automatic control while high-pressure air exits the highpressure air nozzles to blow off any powder 28 accumulated on theexternal surfaces of guns 48. Additional details of such high pressureair nozzles that clean guns 48 can be found in U.S. Pat. No. 5,759,271,which is incorporated by reference herein.

[0086] Returning again particularly to FIGS. 16-18, powder station 300includes an assembly 342 of tubes 346 and a plurality of suction hoses344 that extend between the upper ends of tubes 346 and respective guns48. Tubes 346 that are provided in two groups mounted on respectivestabilizing bars 348 as illustrated in FIGS. 17 and 18. Tube assembly342 further includes a lift bracket 350 coupled to the upper ends oftubes 346.

[0087] Powder station 300 includes a guide 352 and a lift assembly 354.Lift assembly 354 includes a pair of lift actuators 356 includingcylinders 358 coupled to guide 352 and rods 360 that extend and retractrelative to cylinders 358. Lift assembly 354 further includes a slider362 coupled to upper ends of rods 360. Bracket 350 is coupled to slider362 by flange 364. Slider 362 moves upwardly on guide structure 352 whenrods 360 are extended out of cylinders 358 and slider 362 movesdownwardly on guide structure 352 when rods 360 are retracted intocylinders 358. Flange 364, bracket 350, tubes 346, and bars 348 movewith slider 362 as slider moves upwardly and downwardly.

[0088] During powder coating operations, the lower ends of tubes 342 arelowered into the mass of powder 28 contained in container 312 andsuction is applied to tubes 342 and hoses 344 to extract powder 28 outof container 312 and deliver the extracted powder 28 to guns 48. Duringa color change operation, an operator enters a command on input device326 to lift tube assembly 342 upwardly out of container 312 as indicatedby arrow 366 in FIG. 17. After tube assembly 342 is lifted out ofcontainer 312, container 312 is removed from shelf 314. The operatorremoves the bottom end of hose 316 from container 312 , and then removescontainer 312 from shelf 314.

[0089] Powder coating station 300 includes a plurality of high-pressureair nozzles 368, each of which is aligned with an opening in acorresponding tube 346 as illustrated in FIG. 17. Nozzles 368 areprovided openings 369 formed in shelf 314. The ends of nozzles 368 areeither substantially coplanar with or slightly below shelf 314. Aftercontainer 312 is removed from shelf 314, the operator enters a commandon input device 326 to lower tube assembly 342 downwardly from a raisedposition, illustrated in FIG. 17, to a lowered position, illustrated inFIG. 18. When tube assembly 342 is in the lowered position, each nozzle368 registers with opening in respective tube 346. Then, high-pressureair is supplied through nozzles 368 to clean powder 28 from the internalpassages of tubes 346, hoses 344, and guns 48. After a time, thehigh-pressure air is turned off and tube assembly 342 is lifted fromnozzles 368 to the raised position illustrated in FIG. 17.

[0090] While tubes 346, hoses 344, and guns 48 are being cleaned, theoperator can disassemble sieve 310 and clean filter screen 318 andportions 317, 319 using, for example, a high-pressure air gun 367,illustrated in FIG. 18. If desired, after disconnection of hoses 280from ports 118 of a cart 54 and before removal of the end of hose 316from container 312, the operator may insert air gun 367 into the ends ofthe hoses 280 disconnected from ports 118 and direct high-pressure airthrough hoses 280 to blow any powder 28 remaining in hoses 280 throughsieve 310 and into container 312. Alternatively, the operator mayreplace hoses 280 with clean ones during color change operations andforego using air gun 367 to clean the hoses 280 being replaced. Theoperator cleaning powder station 300 may also will use a cloth or thelike to wipe down external surfaces of the various pieces of equipment,such as sieve 310, tube assembly, and lift assembly 354.

[0091] After powder station 300 is cleaned, a replacement container 312that contains powder of a different color is placed on shelf 314 and theoperator enters a command on input device 326 to lower tube assembly 342into the replacement container 312. Then, once the operator cleaningpowder station 300 confirms that no one is in booth 10 and that booth 10and second cart 54 are ready for powder coating operations, the operatorenters commands on input device 326 to resume the powder coatingoperations.

[0092] Powder coating system 30 includes at least one spray-to-wasteequipment module or cart 370 as illustrated in FIGS. 1 and 2. Cart 370is placed in equipment-receiving space 24 when no powder 28 is to berecovered for reuse during powder coating operations. Cart 370 issimilar to carts 54 and therefore, like reference numerals are used todenote components of cart 370 that are substantially the same as likecomponents of carts 54. The main difference between cart 370 and carts54 is that cart 370 does not include any separators or hoppers.

[0093] Cart 370 includes a rectangular bottom panel 372 and a pair ofend panels 374 extending upwardly from bottom panel 372. Cart 370further includes a pair of frame members 376 extending longitudinallybetween the upper corners of end panels 374 and a set of vertical framemembers 378 extending between frame members 376 and bottom panel 372 forstability. Ducts 60 are coupled to end panels 374 with clamping devicesthat are the same as the clamping devices used in carts 54 to coupleducts 60 to separator assembly 58. Cart 370 is configured so that anempty space 380 is defined above bottom panel 372 between end panels374. The inner passages of ducts 60 are in fluid-flow communication withempty space 380 through openings defined beneath frame members 376 andbetween frame members 378.

[0094] When cart 370 is received in space 24 and lifted to a raisedposition by actuators 220, empty space 380 is in fluid-flowcommunication with air plenum 244. In some embodiments, gaskets orsealing members are interposed between bottom surface 246 of air plenum244 and the upper surfaces of frame members 376 and end panels 374 ofcart 370.

[0095] When spray-to-waste cart 370 is received in space 24, the airpowder mixture 29 is drawn by fan 262 through openings 188 formed inbottom wall 18 of booth 10, through ducts 60, through empty space 380 ofcart 370, through duct work 260, and into housing 261. After air-powdermixture 29 reaches housing 261, fans 262 draw air-powder mixture 29through filters 270 of filter section 274 so that powder 28 is filteredout of air-powder mixture 29. The powder 28 filtered out of air-powdermixture 29 is blown downwardly to waste hopper 277 by the cleaningsystem of air circulation equipment 258 for collection and disposal.When cart 370 is received in space 24, air circulation equipment 258 canbe operated to draw air through booth 10, cart 370, air plenum 244, andductwork 260 at a higher flow rate than when any of carts 54 arereceived in space 24.

[0096] Although the invention has been described in detail withreference to certain preferred embodiments, variations and modificationsexist within the scope and spirit of the invention as described anddefined in the following claims.

What is claimed is:
 1. A powder coating system that operates to dispensepowder onto objects to be coated by the powder, the powder coatingsystem including a separator assembly for removing powder from anair-powder mixture, a booth in which objects are to be coated withpowder, the booth having a bottom wall that overlies the separatorassembly, the bottom wall being formed to include an opening throughwhich the air-powder mixture moves into the separator assembly, and ahopper assembly underlying the separator assembly, the powder removedfrom the air-powder mixture in the separator assembly migratingdownwardly to the hopper assembly.
 2. The powder coating system of claim1 wherein the hopper assembly includes wheels for facilitating movementof the hopper assembly from under the bottom wall.
 3. The powder coatingsystem of claim 2 wherein the separator assembly is carried by thehopper assembly.
 4. The powder coating system of claim 1 furtherincluding powder-delivery equipment for supplying powder for coatingobjects, the hopper assembly including powder-transfer equipment fortransferring recovered powder from the hopper assembly to thepowder-delivery equipment.
 5. The powder coating system of claim 4wherein the powder-transfer equipment includes at least one venturipump.
 6. The powder coating system of claim 4 wherein thepowder-delivery equipment includes a powder dispenser configured todispense powder toward objects in the booth and a powder station thatreceives powder recovered from the hopper assembly and that supplies therecovered powder to the powder dispenser.
 7. The powder coating systemof claim 6 wherein the powder-delivery equipment includes areciprocator, the powder dispenser coupled to the reciprocator to changethe position of the powder dispenser relative to the booth.
 8. Thepowder coating system of claim 1 further including air circulationequipment for drawing the air-powder mixture from the booth, through theopening, and into the separator assembly.
 9. The powder coating systemof claim 8 wherein the air circulation equipment includes a filter, theair drawn away from the separator assembly passing through the filterand discharging to atmosphere.
 10. The powder coating system of claim 8including an air duct for providing a passage between the booth and theseparator assembly and between the separator assembly and the aircirculation equipment, the air duct coupled to the bottom wall.
 11. Apowder coating system permitting for quick color changes, the powdercoating system operating to dispense powder onto objects to be coated bythe powder and including a booth in which objects are oriented forpowder coating, the booth including a bottom wall beneath which isdefined an equipment-receiving space, the bottom wall including anopening through which an air-powder mixture moves from the booth, and aplurality of powder-recovery modules, the powder-recovery modules beingselectively and interchangeably insertable into the equipment-receivingspace to receive the air-powder mixture through the opening.
 12. Thepowder coating system of claim 11 wherein each of the powder-recoverymodules includes a hopper assembly and a separator assembly coupled tothe hopper assembly.
 13. The powder coating system of claim 12 whereineach of the powder-recovery modules includes wheels to facilitateselective and interchangeable insertion of the powder-recovery modulesinto the equipment-receiving space.
 14. The powder coating system ofclaim 12 wherein the separator assembly of each powder-recoveryequipment module is above a respective hopper assembly.
 15. The powdercoating system of claim 11 further including powder-delivery equipmentfor supplying powder for coating objects, each of the powder-recoverymodules including powder-transfer equipment for transferring recoveredpowder from the respective powder-recovery module to the powder-deliveryequipment.
 16. The powder coating system of claim 15 wherein thepowder-transfer equipment includes a venturi pump.
 17. The powdercoating system of claim 15 wherein the powder-delivery equipmentincludes a powder dispenser for dispensing powder into the booth and apowder station for receives powder from the powder-recovery modulereceived in the equipment-receiving space and supplying the recoveredpowder to the powder dispenser.
 18. The powder coating system of claim17 further including a reciprocator, the powder dispenser coupled to thereciprocator to be reciprocated thereby.
 19. The powder coating systemof claim 11 further including air circulation equipment for drawing theair-powder mixture from the booth, through the opening, and into thepowder-recovery module received in the equipment-receiving space. 20.The powder coating system of claim 19 wherein the air circulationequipment includes a filter, the air circulation equipment drawing theair-powder mixture from the booth, through the opening, and into thepowder-recovery module received in the equipment-receiving space, aircontaining unrecovered powder passing through the filter and filteredair then being discharged to atmosphere.
 21. The powder coating systemof claim 19 wherein the booth includes an air duct coupled to the bottomwall and the air duct provides a passage between the powder-recoverymodule received in the equipment-receiving space and the air circulationequipment.
 22. The powder coating system of claim 21, wherein at least aportion of the air duct is between the bottom wall and thepowder-recovery module received in the equipment-receiving space.
 23. Amethod of changing a powder coating system that operates to dispensepowder onto objects to be coated by the powder from coating objects withpowder of a first color to coating objects with powder of a secondcolor, the method including removing from an equipment-receiving spacedefined beneath a bottom wall of a booth a first powder-recovery moduleassociated with coating objects with powder of the first color, andpositioning in the equipment-receiving space a second powder-recoverymodule associated with coating objects with powder of the second color.24. The method of claim 23 wherein removing the first powder-recoverymodule includes removing from the equipment-receiving space a separatorassembly of the first powder-recovery module.
 25. The method of claim 24wherein removing the first powder-recovery module includes removing fromthe equipment-receiving space a hopper assembly of the firstpowder-recovery module that is coupled to the separator assembly. 26.The method of claim 23 further including decoupling the firstpowder-recovery module from a powder station that is to receiverecovered powder from the first powder-recovery module when objects arebeing coated with powder of the first color.
 27. The method of claim 23further including turning off a vibrator of the first powder-recoverymodule.
 28. The method of claim 23 wherein removing the firstpowder-recovery module includes lowering the first powder-recoverymodule away from the bottom wall.
 29. The method of claim 28 whereinlowering the first powder-recovery module away from the bottom wallincludes operating an actuator to lower the first powder-recovery moduleaway from the bottom wall.
 30. The method of claim 23 wherein removingthe first powder-recovery module includes lowering the firstpowder-recovery module away from the bottom wall and then withdrawingthe first powder-recovery module from the equipment-receiving spacealong a substantially horizontal path.
 31. The method of claim 23wherein positioning the second powder-recovery module includespositioning in the equipment-receiving space a separator assembly of thesecond powder-recovery module.
 32. The method of claim 31 whereinpositioning the second powder-recovery module includes positioning inthe equipment-receiving space a hopper assembly of the secondpowder-recovery module that is coupled to the separator assembly. 33.The method of claim 23 further including coupling the secondpowder-recovery module to a powder station that is to receive recoveredpowder from the second powder-recovery module when objects are beingcoated with powder of the second color.
 34. The method of claim 23further including turning on a vibrator of the second powder-recoverymodule.
 35. The method of claim 23 wherein positioning a secondpowder-recovery module includes raising the second powder-recoverymodule toward the bottom wall.
 36. The method of claim 35 whereinraising the second powder-recovery module includes operating an actuatorto move the second powder-recovery module into a raised position. 37.The method of claim 23 wherein positioning a second powder-recoverymodule includes moving the second powder-recovery module into theequipment-receiving space along a substantially horizontal path and thenraising the second powder-recovery module toward the bottom wall. 38.The method of claim 23 further including closing an opening formed inthe bottom wall after removing the first powder-recovery module.
 39. Themethod of claim 38 further including cleaning walls of the booth afterclosing the opening formed in the bottom wall.
 40. The method of claim39 further including opening the opening after cleaning walls of thebooth and before positioning the second powder-recovery module.